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* wal stats questions @ 2021-03-24 23:22 Andres Freund <[email protected]> 0 siblings, 1 reply; 8698+ messages in thread From: Andres Freund @ 2021-03-24 23:22 UTC (permalink / raw) To: pgsql-hackers; Fujii Masao <[email protected]>; Masahiro Ikeda <[email protected]> Hi, I got a few questions about the wal stats while working on the shmem stats patch: 1) What is the motivation to have both prevWalUsage and pgWalUsage, instead of just accumulating the stats since the last submission? There doesn't seem to be any comment explaining it? Computing differences to previous values, and copying to prev*, isn't free. I assume this is out of a fear that the stats could get reset before they're used for instrument.c purposes - but who knows? 2) Why is there both pgstat_send_wal() and pgstat_report_wal()? With the former being used by wal writer, the latter by most other processes? There again don't seem to be comments explaining this. 3) Doing if (memcmp(&WalStats, &all_zeroes, sizeof(PgStat_MsgWal)) == 0) just to figure out if there's been any changes isn't all that cheap. This is regularly exercised in read-only workloads too. Seems adding a boolean WalStats.have_pending = true or such would be better. 4) For plain backends pgstat_report_wal() is called by pgstat_report_stat() - but it is not checked as part of the "Don't expend a clock check if nothing to do" check at the top. It's probably rare to have pending wal stats without also passing one of the other conditions, but ... Generally the various patches seems to to have a lot of the boilerplate style comments (like "Prepare and send the message"), but very little in the way of explaining the design. Greetings, Andres Freund ^ permalink raw reply [nested|flat] 8698+ messages in thread
* Re: wal stats questions @ 2021-03-25 01:51 Masahiro Ikeda <[email protected]> parent: Andres Freund <[email protected]> 0 siblings, 1 reply; 8698+ messages in thread From: Masahiro Ikeda @ 2021-03-25 01:51 UTC (permalink / raw) To: Andres Freund <[email protected]>; pgsql-hackers; Fujii Masao <[email protected]> On 2021/03/25 8:22, Andres Freund wrote: > Hi, > > I got a few questions about the wal stats while working on the shmem > stats patch: Thanks for your reviews. > 1) What is the motivation to have both prevWalUsage and pgWalUsage, > instead of just accumulating the stats since the last submission? > There doesn't seem to be any comment explaining it? Computing > differences to previous values, and copying to prev*, isn't free. I > assume this is out of a fear that the stats could get reset before > they're used for instrument.c purposes - but who knows? Is your point that it's better to call pgWalUsage = 0; after sending the stats? My understanding is as same as your assumption. For example, pg_stat_statements.c use pgWalUsage and calculate the diff. But, because the stats may be sent after the transaction is finished, it doesn't seem to lead wrong stats if pgWalUsage = 0 is called. So, I agree your suggestion. If the extension wants to know the walusage diff across two transactions, it may lead to wrong stats, but I think it won't happen. > 2) Why is there both pgstat_send_wal() and pgstat_report_wal()? With the > former being used by wal writer, the latter by most other processes? > There again don't seem to be comments explaining this. To control the transmission interval for the wal writer because it may send the stats too frequency, and to omit to calculate the generated wal stats because it doesn't generate wal records. But, now I think it's better to merge them. > 3) Doing if (memcmp(&WalStats, &all_zeroes, sizeof(PgStat_MsgWal)) == 0) > just to figure out if there's been any changes isn't all that > cheap. This is regularly exercised in read-only workloads too. Seems > adding a boolean WalStats.have_pending = true or such would be > better. I understood that for backends, this may leads performance degradation and this problem is not only for the WalStats but also SLRUStats. I wondered the degradation is so big because pgstat_report_stat() checks if at least PGSTAT_STAT_INTERVAL msec is passed since it last sent before check the diff. If my understanding is correct, to get timestamp is more expensive. > 4) For plain backends pgstat_report_wal() is called by > pgstat_report_stat() - but it is not checked as part of the "Don't > expend a clock check if nothing to do" check at the top. It's > probably rare to have pending wal stats without also passing one of > the other conditions, but ... (I'm not confidence my understanding of your comment is right.) You mean that we need to expend a clock check in pgstat_report_wal()? I think it's unnecessary because pgstat_report_stat() is already checked it. > Generally the various patches seems to to have a lot of the boilerplate > style comments (like "Prepare and send the message"), but very little in > the way of explaining the design. Sorry for that. I'll be careful. Regards, -- Masahiro Ikeda NTT DATA CORPORATION ^ permalink raw reply [nested|flat] 8698+ messages in thread
* Re: wal stats questions @ 2021-03-25 04:07 Andres Freund <[email protected]> parent: Masahiro Ikeda <[email protected]> 0 siblings, 1 reply; 8698+ messages in thread From: Andres Freund @ 2021-03-25 04:07 UTC (permalink / raw) To: Masahiro Ikeda <[email protected]>; +Cc: pgsql-hackers; Fujii Masao <[email protected]> Hi, On 2021-03-25 10:51:56 +0900, Masahiro Ikeda wrote: > On 2021/03/25 8:22, Andres Freund wrote: > > 1) What is the motivation to have both prevWalUsage and pgWalUsage, > > instead of just accumulating the stats since the last submission? > > There doesn't seem to be any comment explaining it? Computing > > differences to previous values, and copying to prev*, isn't free. I > > assume this is out of a fear that the stats could get reset before > > they're used for instrument.c purposes - but who knows? > > Is your point that it's better to call pgWalUsage = 0; after sending the > stats? Yes. At least there should be a comment explaining why it's done the way it is. > > 3) Doing if (memcmp(&WalStats, &all_zeroes, sizeof(PgStat_MsgWal)) == 0) > > just to figure out if there's been any changes isn't all that > > cheap. This is regularly exercised in read-only workloads too. Seems > > adding a boolean WalStats.have_pending = true or such would be > > better. > > I understood that for backends, this may leads performance degradation and > this problem is not only for the WalStats but also SLRUStats. > > I wondered the degradation is so big because pgstat_report_stat() checks if at > least PGSTAT_STAT_INTERVAL msec is passed since it last sent before check the > diff. If my understanding is correct, to get timestamp is more expensive. Getting a timestamp is expensive, yes. But I think we need to check for the no-pending-wal-stats *before* the clock check. See the below: > > 4) For plain backends pgstat_report_wal() is called by > > pgstat_report_stat() - but it is not checked as part of the "Don't > > expend a clock check if nothing to do" check at the top. It's > > probably rare to have pending wal stats without also passing one of > > the other conditions, but ... > > (I'm not confidence my understanding of your comment is right.) > You mean that we need to expend a clock check in pgstat_report_wal()? > I think it's unnecessary because pgstat_report_stat() is already checked it. No, I mean that right now we might can erroneously return early pgstat_report_wal() for normal backends in some workloads: void pgstat_report_stat(bool disconnect) ... /* Don't expend a clock check if nothing to do */ if ((pgStatTabList == NULL || pgStatTabList->tsa_used == 0) && pgStatXactCommit == 0 && pgStatXactRollback == 0 && !have_function_stats && !disconnect) return; might return if there only is pending WAL activity. This needs to check whether there are pending WAL stats. Which in turn means that the check should be fast. Greetings, Andres Freund ^ permalink raw reply [nested|flat] 8698+ messages in thread
* Re: wal stats questions @ 2021-03-25 07:37 Kyotaro Horiguchi <[email protected]> parent: Andres Freund <[email protected]> 0 siblings, 2 replies; 8698+ messages in thread From: Kyotaro Horiguchi @ 2021-03-25 07:37 UTC (permalink / raw) To: [email protected]; +Cc: [email protected]; pgsql-hackers; [email protected] At Wed, 24 Mar 2021 21:07:26 -0700, Andres Freund <[email protected]> wrote in > Hi, > > On 2021-03-25 10:51:56 +0900, Masahiro Ikeda wrote: > > On 2021/03/25 8:22, Andres Freund wrote: > > > 1) What is the motivation to have both prevWalUsage and pgWalUsage, > > > instead of just accumulating the stats since the last submission? > > > There doesn't seem to be any comment explaining it? Computing > > > differences to previous values, and copying to prev*, isn't free. I > > > assume this is out of a fear that the stats could get reset before > > > they're used for instrument.c purposes - but who knows? > > > > Is your point that it's better to call pgWalUsage = 0; after sending the > > stats? > > Yes. At least there should be a comment explaining why it's done the way > it is. pgWalUsage was used without resetting and we (I) thought that that behavior should be preserved. On second thought, as Andres suggested, we can just reset pgWalUsage at sending since AFAICS no one takes difference crossing pgstat_report_stat() calls. > > > 3) Doing if (memcmp(&WalStats, &all_zeroes, sizeof(PgStat_MsgWal)) == 0) > > > just to figure out if there's been any changes isn't all that > > > cheap. This is regularly exercised in read-only workloads too. Seems > > > adding a boolean WalStats.have_pending = true or such would be > > > better. > > > > I understood that for backends, this may leads performance degradation and > > this problem is not only for the WalStats but also SLRUStats. > > > > I wondered the degradation is so big because pgstat_report_stat() checks if at > > least PGSTAT_STAT_INTERVAL msec is passed since it last sent before check the > > diff. If my understanding is correct, to get timestamp is more expensive. > > Getting a timestamp is expensive, yes. But I think we need to check for > the no-pending-wal-stats *before* the clock check. See the below: > > > > > 4) For plain backends pgstat_report_wal() is called by > > > pgstat_report_stat() - but it is not checked as part of the "Don't > > > expend a clock check if nothing to do" check at the top. It's > > > probably rare to have pending wal stats without also passing one of > > > the other conditions, but ... > > > > (I'm not confidence my understanding of your comment is right.) > > You mean that we need to expend a clock check in pgstat_report_wal()? > > I think it's unnecessary because pgstat_report_stat() is already checked it. > > No, I mean that right now we might can erroneously return early > pgstat_report_wal() for normal backends in some workloads: > > void > pgstat_report_stat(bool disconnect) > ... > /* Don't expend a clock check if nothing to do */ > if ((pgStatTabList == NULL || pgStatTabList->tsa_used == 0) && > pgStatXactCommit == 0 && pgStatXactRollback == 0 && > !have_function_stats && !disconnect) > return; > > might return if there only is pending WAL activity. This needs to check > whether there are pending WAL stats. Which in turn means that the check > should be fast. Agreed that the condition is wrong. On the other hand, the counters are incremented in XLogInsertRecord() and I think we don't want add instructions there. If any wal activity has been recorded, wal_records is always positive thus we can check for wal activity just by "pgWalUsage.wal_records > 0, which should be fast enough. regards. -- Kyotaro Horiguchi NTT Open Source Software Center ^ permalink raw reply [nested|flat] 8698+ messages in thread
* Re: wal stats questions @ 2021-03-25 10:01 Fujii Masao <[email protected]> parent: Kyotaro Horiguchi <[email protected]> 1 sibling, 1 reply; 8698+ messages in thread From: Fujii Masao @ 2021-03-25 10:01 UTC (permalink / raw) To: Kyotaro Horiguchi <[email protected]>; [email protected]; +Cc: [email protected]; pgsql-hackers On 2021/03/25 16:37, Kyotaro Horiguchi wrote: > At Wed, 24 Mar 2021 21:07:26 -0700, Andres Freund <[email protected]> wrote in >> Hi, >> >> On 2021-03-25 10:51:56 +0900, Masahiro Ikeda wrote: >>> On 2021/03/25 8:22, Andres Freund wrote: >>>> 1) What is the motivation to have both prevWalUsage and pgWalUsage, >>>> instead of just accumulating the stats since the last submission? >>>> There doesn't seem to be any comment explaining it? Computing >>>> differences to previous values, and copying to prev*, isn't free. I >>>> assume this is out of a fear that the stats could get reset before >>>> they're used for instrument.c purposes - but who knows? >>> >>> Is your point that it's better to call pgWalUsage = 0; after sending the >>> stats? >> >> Yes. At least there should be a comment explaining why it's done the way >> it is. > > pgWalUsage was used without resetting and we (I) thought that that > behavior should be preserved. On second thought, as Andres suggested, > we can just reset pgWalUsage at sending since AFAICS no one takes > difference crossing pgstat_report_stat() calls. Yes, I agree that we can do that since there seems no such code for now. Also if we do that, we can check, for example "pgWalUsage.wal_records > 0" as you suggested, to easily determine whether there is pending WAL stats or not. Anyway I agree it's better to add comments about the design more. >>>> 3) Doing if (memcmp(&WalStats, &all_zeroes, sizeof(PgStat_MsgWal)) == 0) >>>> just to figure out if there's been any changes isn't all that >>>> cheap. This is regularly exercised in read-only workloads too. Seems >>>> adding a boolean WalStats.have_pending = true or such would be >>>> better. >>> >>> I understood that for backends, this may leads performance degradation and >>> this problem is not only for the WalStats but also SLRUStats. >>> >>> I wondered the degradation is so big because pgstat_report_stat() checks if at >>> least PGSTAT_STAT_INTERVAL msec is passed since it last sent before check the >>> diff. If my understanding is correct, to get timestamp is more expensive. >> >> Getting a timestamp is expensive, yes. But I think we need to check for >> the no-pending-wal-stats *before* the clock check. See the below: >> >> >>>> 4) For plain backends pgstat_report_wal() is called by >>>> pgstat_report_stat() - but it is not checked as part of the "Don't >>>> expend a clock check if nothing to do" check at the top. It's >>>> probably rare to have pending wal stats without also passing one of >>>> the other conditions, but ... >>> >>> (I'm not confidence my understanding of your comment is right.) >>> You mean that we need to expend a clock check in pgstat_report_wal()? >>> I think it's unnecessary because pgstat_report_stat() is already checked it. >> >> No, I mean that right now we might can erroneously return early >> pgstat_report_wal() for normal backends in some workloads: >> >> void >> pgstat_report_stat(bool disconnect) >> ... >> /* Don't expend a clock check if nothing to do */ >> if ((pgStatTabList == NULL || pgStatTabList->tsa_used == 0) && >> pgStatXactCommit == 0 && pgStatXactRollback == 0 && >> !have_function_stats && !disconnect) >> return; >> >> might return if there only is pending WAL activity. This needs to check >> whether there are pending WAL stats. Which in turn means that the check >> should be fast. > > Agreed that the condition is wrong. On the other hand, the counters > are incremented in XLogInsertRecord() and I think we don't want add > instructions there. Basically yes. We should avoid that especially while WALInsertLock is being hold. But it's not so harmful to do that after the lock is released? > If any wal activity has been recorded, wal_records is always positive > thus we can check for wal activity just by "pgWalUsage.wal_records > > 0, which should be fast enough. Maybe there is the case where a backend generates no WAL records, but just writes them because it needs to do write-ahead-logging when flush the table data? If yes, "pgWalUsage.wal_records > 0" is not enough. Probably other fields also need to be checked. Regards, -- Fujii Masao Advanced Computing Technology Center Research and Development Headquarters NTT DATA CORPORATION ^ permalink raw reply [nested|flat] 8698+ messages in thread
* Re: wal stats questions @ 2021-03-26 01:08 Kyotaro Horiguchi <[email protected]> parent: Fujii Masao <[email protected]> 0 siblings, 1 reply; 8698+ messages in thread From: Kyotaro Horiguchi @ 2021-03-26 01:08 UTC (permalink / raw) To: [email protected]; +Cc: [email protected]; [email protected]; pgsql-hackers At Thu, 25 Mar 2021 19:01:23 +0900, Fujii Masao <[email protected]> wrote in > On 2021/03/25 16:37, Kyotaro Horiguchi wrote: > > pgWalUsage was used without resetting and we (I) thought that that > > behavior should be preserved. On second thought, as Andres suggested, > > we can just reset pgWalUsage at sending since AFAICS no one takes > > difference crossing pgstat_report_stat() calls. > > Yes, I agree that we can do that since there seems no such code for > now. > Also if we do that, we can check, for example "pgWalUsage.wal_records > > 0" > as you suggested, to easily determine whether there is pending WAL > stats or not. > Anyway I agree it's better to add comments about the design more. ... > > If any wal activity has been recorded, wal_records is always positive > > thus we can check for wal activity just by "pgWalUsage.wal_records > > > 0, which should be fast enough. > > Maybe there is the case where a backend generates no WAL records, > but just writes them because it needs to do write-ahead-logging > when flush the table data? If yes, "pgWalUsage.wal_records > 0" is not > enough. > Probably other fields also need to be checked. (I noticed I made the discussion above unconsciously premising pgWalUsage reset.) I may be misunderstanding or missing something, but the only place where pgWalUsage counters are increased is XLogInsertRecrod. That is, pgWalUsage counts wal insertions, not writes nor flushes. AFAICS pgWalUsage.wal_records is always incremented when other counters are increased. Looking from another side, we should refrain from adding counters that incrases at a different time than pgWalUsage.wal_recrods. (That should be written as a comment there.) regards. -- Kyotaro Horiguchi NTT Open Source Software Center ^ permalink raw reply [nested|flat] 8698+ messages in thread
* Re: wal stats questions @ 2021-03-26 01:32 Fujii Masao <[email protected]> parent: Kyotaro Horiguchi <[email protected]> 0 siblings, 1 reply; 8698+ messages in thread From: Fujii Masao @ 2021-03-26 01:32 UTC (permalink / raw) To: Kyotaro Horiguchi <[email protected]>; +Cc: [email protected]; [email protected]; pgsql-hackers On 2021/03/26 10:08, Kyotaro Horiguchi wrote: > At Thu, 25 Mar 2021 19:01:23 +0900, Fujii Masao <[email protected]> wrote in >> On 2021/03/25 16:37, Kyotaro Horiguchi wrote: >>> pgWalUsage was used without resetting and we (I) thought that that >>> behavior should be preserved. On second thought, as Andres suggested, >>> we can just reset pgWalUsage at sending since AFAICS no one takes >>> difference crossing pgstat_report_stat() calls. >> >> Yes, I agree that we can do that since there seems no such code for >> now. >> Also if we do that, we can check, for example "pgWalUsage.wal_records >>> 0" >> as you suggested, to easily determine whether there is pending WAL >> stats or not. >> Anyway I agree it's better to add comments about the design more. > ... >>> If any wal activity has been recorded, wal_records is always positive >>> thus we can check for wal activity just by "pgWalUsage.wal_records > >>> 0, which should be fast enough. >> >> Maybe there is the case where a backend generates no WAL records, >> but just writes them because it needs to do write-ahead-logging >> when flush the table data? If yes, "pgWalUsage.wal_records > 0" is not >> enough. >> Probably other fields also need to be checked. > > (I noticed I made the discussion above unconsciously premising > pgWalUsage reset.) > > I may be misunderstanding or missing something, but the only place > where pgWalUsage counters are increased is XLogInsertRecrod. That is, > pgWalUsage counts wal insertions, not writes nor flushes. AFAICS Yes. And WalStats instead of pgWalUsage includes the stats about not only WAL insertions, but also writes and flushes. pgstat_send_wal() checks WalStats to determine whether there are pending WAL stats to send to the stats collector or not. That is, the counters of not only WAL insertions but also writes and flushes should be checked to determine whether there are pending stats or not, I think.. Regards, -- Fujii Masao Advanced Computing Technology Center Research and Development Headquarters NTT DATA CORPORATION ^ permalink raw reply [nested|flat] 8698+ messages in thread
* Re: wal stats questions @ 2021-03-26 03:47 Kyotaro Horiguchi <[email protected]> parent: Fujii Masao <[email protected]> 0 siblings, 1 reply; 8698+ messages in thread From: Kyotaro Horiguchi @ 2021-03-26 03:47 UTC (permalink / raw) To: [email protected]; +Cc: [email protected]; [email protected]; pgsql-hackers At Fri, 26 Mar 2021 10:32:23 +0900, Fujii Masao <[email protected]> wrote in > > I may be misunderstanding or missing something, but the only place > > where pgWalUsage counters are increased is XLogInsertRecrod. That is, > > pgWalUsage counts wal insertions, not writes nor flushes. AFAICS > > Yes. And WalStats instead of pgWalUsage includes the stats about > not only WAL insertions, but also writes and flushes. Ugh! I was missing a very large blob.. Ok, we need additional check for non-pgWalUsage part. Sorry. > pgstat_send_wal() checks WalStats to determine whether there are > pending WAL stats to send to the stats collector or not. That is, > the counters of not only WAL insertions but also writes and flushes > should be checked to determine whether there are pending stats or not, > I think.. I think we may have an additional flag to notify about io-stat part, in constrast to wal-insertion part . Anyway we do additional INSTR_TIME_SET_CURRENT when track_wal_io_timinge. regards. -- Kyotaro Horiguchi NTT Open Source Software Center ^ permalink raw reply [nested|flat] 8698+ messages in thread
* Re: wal stats questions @ 2021-03-26 07:20 Masahiro Ikeda <[email protected]> parent: Kyotaro Horiguchi <[email protected]> 0 siblings, 1 reply; 8698+ messages in thread From: Masahiro Ikeda @ 2021-03-26 07:20 UTC (permalink / raw) To: Kyotaro Horiguchi <[email protected]>; [email protected]; Andres Freund <[email protected]>; +Cc: pgsql-hackers Thanks for many your suggestions! I made the patch to handle the issues. > 1) What is the motivation to have both prevWalUsage and pgWalUsage, > instead of just accumulating the stats since the last submission? > There doesn't seem to be any comment explaining it? Computing > differences to previous values, and copying to prev*, isn't free. I > assume this is out of a fear that the stats could get reset before > they're used for instrument.c purposes - but who knows? I removed the unnecessary code copying pgWalUsage and just reset the pgWalUsage after reporting the stats in pgstat_report_wal(). > 2) Why is there both pgstat_send_wal() and pgstat_report_wal()? With the > former being used by wal writer, the latter by most other processes? > There again don't seem to be comments explaining this. I added the comments why two functions are separated. (But is it better to merge them?) > 3) Doing if (memcmp(&WalStats, &all_zeroes, sizeof(PgStat_MsgWal)) == 0) > just to figure out if there's been any changes isn't all that > cheap. This is regularly exercised in read-only workloads too. Seems > adding a boolean WalStats.have_pending = true or such would be > better. > 4) For plain backends pgstat_report_wal() is called by > pgstat_report_stat() - but it is not checked as part of the "Don't > expend a clock check if nothing to do" check at the top. It's > probably rare to have pending wal stats without also passing one of > the other conditions, but ... I added the logic to check if the stats counters are updated or not in pgstat_report_stat() using not only generated wal record but also write/sync counters, and it can skip to call reporting function. Although I added the condition which the write/sync counters are updated or not, I haven't understood the following case yet...Sorry. I checked related code and tested to insert large object, but I couldn't. I'll investigate more deeply, but if you already know the function which leads the following case, please let me know. > Maybe there is the case where a backend generates no WAL records, > but just writes them because it needs to do write-ahead-logging > when flush the table data? > Ugh! I was missing a very large blob.. Ok, we need additional check > for non-pgWalUsage part. Sorry. Regards, -- Masahiro Ikeda NTT DATA CORPORATION Attachments: [text/x-patch] v1-0001-performance-improvements-of-reporting-wal-stats.patch (7.1K, ../../[email protected]/2-v1-0001-performance-improvements-of-reporting-wal-stats.patch) download | inline diff: diff --git a/src/backend/executor/instrument.c b/src/backend/executor/instrument.c index 237e13361b..095d8d0970 100644 --- a/src/backend/executor/instrument.c +++ b/src/backend/executor/instrument.c @@ -19,6 +19,17 @@ BufferUsage pgBufferUsage; static BufferUsage save_pgBufferUsage; + +/* + * generated WAL usage counters. + * + * Be careful that the counters are cleared after reporting them to + * the stats collector although you can use WalUsageAccumDiff() + * to computing differences to previous values. For backends, + * the counters may be reset after a transaction is finished and + * pgstat_report_wal() is invoked, so you can compute the difference + * in the same transaction only. + */ WalUsage pgWalUsage; static WalUsage save_pgWalUsage; diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c index 60f45ccc4e..e354a454a9 100644 --- a/src/backend/postmaster/pgstat.c +++ b/src/backend/postmaster/pgstat.c @@ -144,14 +144,6 @@ char *pgstat_stat_tmpname = NULL; PgStat_MsgBgWriter BgWriterStats; PgStat_MsgWal WalStats; -/* - * WAL usage counters saved from pgWALUsage at the previous call to - * pgstat_report_wal(). This is used to calculate how much WAL usage - * happens between pgstat_report_wal() calls, by substracting - * the previous counters from the current ones. - */ -static WalUsage prevWalUsage; - /* * List of SLRU names that we keep stats for. There is no central registry of * SLRUs, so we use this fixed list instead. The "other" entry is used for @@ -879,9 +871,18 @@ pgstat_report_stat(bool disconnect) TabStatusArray *tsa; int i; - /* Don't expend a clock check if nothing to do */ + /* + * Don't expend a clock check if nothing to do. + * + * Note: Regarding the wal data, it's not enough to check only the wal + * records, because there is a case where a backend generates no wal + * records, but just writes them because it needs to do + * write-ahead-logging when flush the table data. + */ if ((pgStatTabList == NULL || pgStatTabList->tsa_used == 0) && pgStatXactCommit == 0 && pgStatXactRollback == 0 && + pgWalUsage.wal_records == 0 && WalStats.m_wal_write == 0 && + WalStats.m_wal_sync == 0 && !have_function_stats && !disconnect) return; @@ -3117,13 +3118,6 @@ pgstat_initialize(void) MyBEEntry = &BackendStatusArray[MaxBackends + MyAuxProcType]; } - /* - * Initialize prevWalUsage with pgWalUsage so that pgstat_report_wal() can - * calculate how much pgWalUsage counters are increased by substracting - * prevWalUsage from pgWalUsage. - */ - prevWalUsage = pgWalUsage; - /* Set up a process-exit hook to clean up */ on_shmem_exit(pgstat_beshutdown_hook, 0); } @@ -4674,28 +4668,40 @@ pgstat_send_bgwriter(void) /* ---------- * pgstat_report_wal() - * - * Calculate how much WAL usage counters are increased and send - * WAL statistics to the collector. + * Send WAL statistics to the collector and clear the counters. * * Must be called by processes that generate WAL. + * + * If needed, the caller should check whether the statistic counters + * are updated, or time interval since we sent is enough before calling + * this function. + * + * Especially, for backends, if they execute read-only transaction, + * they rarely gererate and write the WAL data. So, to call this + * function is no meaning, but it may leads performance degradation. + * + * OTOH, for the checkpointer, it always generates the WAL record and + * doesn't call this function frequently. So, it doesn't need to check + * them. + * + * Note: if you want to know the WAL statistics counters are updated + * or not, to check WalStats.m_wal_records, walStats.wal_write and + * walStats.wal_sync. If WalStats.m_wal_records == 0, walStats.wal_write == 0 + * and WalStats.wal_sync == 0, it means the counters are not updated. + * It's not enough to check only the wal records, because there is a + * case where a backend generates no wal records, but just writes them + * because it needs to do write-ahead-logging when flush the table data. * ---------- */ void pgstat_report_wal(void) { - WalUsage walusage; - /* - * Calculate how much WAL usage counters are increased by substracting the - * previous counters from the current ones. Fill the results in WAL stats - * message. + * set the counters related to generated WAL data. */ - MemSet(&walusage, 0, sizeof(WalUsage)); - WalUsageAccumDiff(&walusage, &pgWalUsage, &prevWalUsage); - - WalStats.m_wal_records = walusage.wal_records; - WalStats.m_wal_fpi = walusage.wal_fpi; - WalStats.m_wal_bytes = walusage.wal_bytes; + WalStats.m_wal_records = pgWalUsage.wal_records; + WalStats.m_wal_fpi = pgWalUsage.wal_fpi; + WalStats.m_wal_bytes = pgWalUsage.wal_bytes; /* * Send WAL stats message to the collector. @@ -4704,18 +4710,25 @@ pgstat_report_wal(void) return; /* - * Save the current counters for the subsequent calculation of WAL usage. + * Clear out the statistics buffer for generated WAL data, so it can be + * re-used. + * + * It's ok because no one takes difference crossing pgstat_report_stat() + * calls although these counters are used in another places, for example + * in pg_stat_statements.c. */ - prevWalUsage = pgWalUsage; + MemSet(&pgWalUsage, 0, sizeof(WalUsage)); } /* ---------- * pgstat_send_wal() - * - * Send WAL statistics to the collector. + * Send WAL statistics to the collector. * - * If 'force' is not set, WAL stats message is only sent if enough time has - * passed since last one was sent to reach PGSTAT_STAT_INTERVAL. + * If the processes that generate WAL data must call pgstat_report_wal() instead. + * + * If 'force' is not set, WAL stats message is only sent if the statistics counters + * are updated and enough time has passed since last one was sent to reach PGSTAT_STAT_INTERVAL. * * Return true if the message is sent, and false otherwise. * ---------- @@ -4723,26 +4736,28 @@ pgstat_report_wal(void) bool pgstat_send_wal(bool force) { - /* We assume this initializes to zeroes */ - static const PgStat_MsgWal all_zeroes; static TimestampTz sendTime = 0; - /* - * This function can be called even if nothing at all has happened. In - * this case, avoid sending a completely empty message to the stats - * collector. - */ - if (memcmp(&WalStats, &all_zeroes, sizeof(PgStat_MsgWal)) == 0) - return false; - if (!force) { - TimestampTz now = GetCurrentTimestamp(); + TimestampTz now; + + /* + * First, to check whether the WAL statistics counters are updated. If + * not updated, we can skip getting a timestamp which is expensive. We + * don't need to check all counters of the WAL statistics counters + * because other counters never be incremented if the counts of + * written/synced are zero. + */ + if (walStats.wal_write == 0 && walStats.wal_sync == 0) + return false; /* * Don't send a message unless it's been at least PGSTAT_STAT_INTERVAL - * msec since we last sent one. + * msec since we last sent one to avoid overloading the stats + * collector. */ + now = GetCurrentTimestamp(); if (!TimestampDifferenceExceeds(sendTime, now, PGSTAT_STAT_INTERVAL)) return false; sendTime = now; ^ permalink raw reply [nested|flat] 8698+ messages in thread
* Re: wal stats questions @ 2021-03-26 17:07 Andres Freund <[email protected]> parent: Kyotaro Horiguchi <[email protected]> 1 sibling, 1 reply; 8698+ messages in thread From: Andres Freund @ 2021-03-26 17:07 UTC (permalink / raw) To: Kyotaro Horiguchi <[email protected]>; +Cc: [email protected]; pgsql-hackers; [email protected] Hi, On 2021-03-25 16:37:10 +0900, Kyotaro Horiguchi wrote: > On the other hand, the counters are incremented in XLogInsertRecord() > and I think we don't want add instructions there. I don't really buy this. Setting a boolean to true, in a cacheline you're already touching, isn't that much compared to all the other stuff in there. The branch to check if wal stats timing etc is enabled is much more expensive. I think we should just set a boolean to true and leave it at that. Greetings, Andres Freund ^ permalink raw reply [nested|flat] 8698+ messages in thread
* Re: wal stats questions @ 2021-03-29 02:09 Kyotaro Horiguchi <[email protected]> parent: Andres Freund <[email protected]> 0 siblings, 1 reply; 8698+ messages in thread From: Kyotaro Horiguchi @ 2021-03-29 02:09 UTC (permalink / raw) To: [email protected]; +Cc: [email protected]; pgsql-hackers; [email protected] At Fri, 26 Mar 2021 10:07:45 -0700, Andres Freund <[email protected]> wrote in > Hi, > > On 2021-03-25 16:37:10 +0900, Kyotaro Horiguchi wrote: > > On the other hand, the counters are incremented in XLogInsertRecord() > > and I think we don't want add instructions there. > > I don't really buy this. Setting a boolean to true, in a cacheline > you're already touching, isn't that much compared to all the other stuff > in there. The branch to check if wal stats timing etc is enabled is much > more expensive. I think we should just set a boolean to true and leave > it at that. Hmm. Yes, I agree to you in that opinion. I (remember I) was told not to add even a cycle to the hot path as far as we can avoid when I tried something like that. So I'm happy to +1 for that if it is the consensus here, since it is cleaner. regards. -- Kyotaro Horiguchi NTT Open Source Software Center ^ permalink raw reply [nested|flat] 8698+ messages in thread
* Re: wal stats questions @ 2021-03-29 02:11 Kyotaro Horiguchi <[email protected]> parent: Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Kyotaro Horiguchi @ 2021-03-29 02:11 UTC (permalink / raw) To: [email protected]; +Cc: [email protected]; pgsql-hackers; [email protected] At Mon, 29 Mar 2021 11:09:00 +0900 (JST), Kyotaro Horiguchi <[email protected]> wrote in > At Fri, 26 Mar 2021 10:07:45 -0700, Andres Freund <[email protected]> wrote in > > Hi, > > > > On 2021-03-25 16:37:10 +0900, Kyotaro Horiguchi wrote: > > > On the other hand, the counters are incremented in XLogInsertRecord() > > > and I think we don't want add instructions there. > > > > I don't really buy this. Setting a boolean to true, in a cacheline > > you're already touching, isn't that much compared to all the other stuff > > in there. The branch to check if wal stats timing etc is enabled is much > > more expensive. I think we should just set a boolean to true and leave > > it at that. > > Hmm. Yes, I agree to you in that opinion. I (remember I) was told not It might sound differently.. To be precise, "I had the same opinion with you". > to add even a cycle to the hot path as far as we can avoid when I > tried something like that. > > So I'm happy to +1 for that if it is the consensus here, since it is > cleaner. -- Kyotaro Horiguchi NTT Open Source Software Center ^ permalink raw reply [nested|flat] 8698+ messages in thread
* Re: wal stats questions @ 2021-03-30 00:41 Masahiro Ikeda <[email protected]> parent: Masahiro Ikeda <[email protected]> 0 siblings, 1 reply; 8698+ messages in thread From: Masahiro Ikeda @ 2021-03-30 00:41 UTC (permalink / raw) To: pgsql-hackers; +Cc: [email protected]; Andres Freund <[email protected]>; Kyotaro Horiguchi <[email protected]> I update the patch since there were my misunderstanding points. On 2021/03/26 16:20, Masahiro Ikeda wrote: > Thanks for many your suggestions! > I made the patch to handle the issues. > >> 1) What is the motivation to have both prevWalUsage and pgWalUsage, >> instead of just accumulating the stats since the last submission? >> There doesn't seem to be any comment explaining it? Computing >> differences to previous values, and copying to prev*, isn't free. I >> assume this is out of a fear that the stats could get reset before >> they're used for instrument.c purposes - but who knows? > > I removed the unnecessary code copying pgWalUsage and just reset the > pgWalUsage after reporting the stats in pgstat_report_wal(). I didn't change this. >> 2) Why is there both pgstat_send_wal() and pgstat_report_wal()? With the >> former being used by wal writer, the latter by most other processes? >> There again don't seem to be comments explaining this. > > I added the comments why two functions are separated. > (But is it better to merge them?) I updated the comments for following reasons. >> 3) Doing if (memcmp(&WalStats, &all_zeroes, sizeof(PgStat_MsgWal)) == 0) >> just to figure out if there's been any changes isn't all that >> cheap. This is regularly exercised in read-only workloads too. Seems >> adding a boolean WalStats.have_pending = true or such would be >> better. >> 4) For plain backends pgstat_report_wal() is called by >> pgstat_report_stat() - but it is not checked as part of the "Don't >> expend a clock check if nothing to do" check at the top. It's >> probably rare to have pending wal stats without also passing one of >> the other conditions, but ... > > I added the logic to check if the stats counters are updated or not in > pgstat_report_stat() using not only generated wal record but also write/sync > counters, and it can skip to call reporting function. I removed the checking code whether the wal stats counters were updated or not in pgstat_report_stat() since I couldn't understand the valid case yet. pgstat_report_stat() is called by backends when the transaction is finished. This means that the condition seems always pass. I thought to implement if the WAL stats counters were not updated, skip to send all statistics including the counters for databases and so on. But I think it's not good because it may take more time to be reflected the generated stats by read-only transaction. > Although I added the condition which the write/sync counters are updated or > not, I haven't understood the following case yet...Sorry. I checked related > code and tested to insert large object, but I couldn't. I'll investigate more > deeply, but if you already know the function which leads the following case, > please let me know. I understood the above case (Fujii-san, thanks for your advice in person). When to flush buffers, for example, to select buffer replacement victim, it requires a WAL flush if the buffer is dirty. So, to check the WAL stats counters are updated or not, I check the number of generated wal record and the counter of syncing in pgstat_report_wal(). The reason why not to check the counter of writing is that if to write is happened, to sync is happened too in the above case. I added the comments in the patch. Regards, -- Masahiro Ikeda NTT DATA CORPORATION Attachments: [text/x-patch] v2-0001-performance-improvements-of-reporting-wal-stats.patch (6.6K, ../../[email protected]/2-v2-0001-performance-improvements-of-reporting-wal-stats.patch) download | inline diff: diff --git a/src/backend/executor/instrument.c b/src/backend/executor/instrument.c index 237e13361b..095d8d0970 100644 --- a/src/backend/executor/instrument.c +++ b/src/backend/executor/instrument.c @@ -19,6 +19,17 @@ BufferUsage pgBufferUsage; static BufferUsage save_pgBufferUsage; + +/* + * generated WAL usage counters. + * + * Be careful that the counters are cleared after reporting them to + * the stats collector although you can use WalUsageAccumDiff() + * to computing differences to previous values. For backends, + * the counters may be reset after a transaction is finished and + * pgstat_report_wal() is invoked, so you can compute the difference + * in the same transaction only. + */ WalUsage pgWalUsage; static WalUsage save_pgWalUsage; diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c index 60f45ccc4e..1ffedb2a24 100644 --- a/src/backend/postmaster/pgstat.c +++ b/src/backend/postmaster/pgstat.c @@ -144,14 +144,6 @@ char *pgstat_stat_tmpname = NULL; PgStat_MsgBgWriter BgWriterStats; PgStat_MsgWal WalStats; -/* - * WAL usage counters saved from pgWALUsage at the previous call to - * pgstat_report_wal(). This is used to calculate how much WAL usage - * happens between pgstat_report_wal() calls, by substracting - * the previous counters from the current ones. - */ -static WalUsage prevWalUsage; - /* * List of SLRU names that we keep stats for. There is no central registry of * SLRUs, so we use this fixed list instead. The "other" entry is used for @@ -3117,13 +3109,6 @@ pgstat_initialize(void) MyBEEntry = &BackendStatusArray[MaxBackends + MyAuxProcType]; } - /* - * Initialize prevWalUsage with pgWalUsage so that pgstat_report_wal() can - * calculate how much pgWalUsage counters are increased by substracting - * prevWalUsage from pgWalUsage. - */ - prevWalUsage = pgWalUsage; - /* Set up a process-exit hook to clean up */ on_shmem_exit(pgstat_beshutdown_hook, 0); } @@ -4674,8 +4659,7 @@ pgstat_send_bgwriter(void) /* ---------- * pgstat_report_wal() - * - * Calculate how much WAL usage counters are increased and send - * WAL statistics to the collector. + * Send WAL statistics to the collector and clear the counters. * * Must be called by processes that generate WAL. * ---------- @@ -4683,19 +4667,36 @@ pgstat_send_bgwriter(void) void pgstat_report_wal(void) { - WalUsage walusage; - /* - * Calculate how much WAL usage counters are increased by substracting the - * previous counters from the current ones. Fill the results in WAL stats - * message. + * Skip if the WAL statistics counters were not updated. + * + * We can know whether the counters were updated to check only two + * records. So, for performance, we don't allocate another memory spaces + * and check the all stats like pgstat_send_slru(). + * + * It's not enough to check only the generated wal records, because there + * is a case that a backend generates no wal records, but just writes and + * syncs the wal data. When to flush buffers, for example, to select + * buffer replacement victim, it requires a WAL flush if the buffer is + * dirty. This happens even if executing read-only transaction. + * + * In this case, if to write is happend, to sync is happend too. although + * there is a case to write is not happend but to sync is happened. For + * example, when to flush buffers just after another process only write + * and don't sync because the wal buffer is no space. + * + * So, it's ok to check the generated wal records and the counter of + * syncing only. */ - MemSet(&walusage, 0, sizeof(WalUsage)); - WalUsageAccumDiff(&walusage, &pgWalUsage, &prevWalUsage); + if (pgWalUsage.wal_records == 0 && WalStats.m_wal_sync == 0) + return; - WalStats.m_wal_records = walusage.wal_records; - WalStats.m_wal_fpi = walusage.wal_fpi; - WalStats.m_wal_bytes = walusage.wal_bytes; + /* + * set the counters related to generated WAL data. + */ + WalStats.m_wal_records = pgWalUsage.wal_records; + WalStats.m_wal_fpi = pgWalUsage.wal_fpi; + WalStats.m_wal_bytes = pgWalUsage.wal_bytes; /* * Send WAL stats message to the collector. @@ -4704,18 +4705,26 @@ pgstat_report_wal(void) return; /* - * Save the current counters for the subsequent calculation of WAL usage. + * Clear out the statistics buffer for generated WAL data, so it can be + * re-used. + * + * It's ok to clear out because no one takes difference crossing + * pgstat_report_wal() calls although these counters are used in another + * places, for example in pg_stat_statements.c. */ - prevWalUsage = pgWalUsage; + MemSet(&pgWalUsage, 0, sizeof(WalUsage)); } /* ---------- * pgstat_send_wal() - * - * Send WAL statistics to the collector. + * Send WAL statistics to the collector. * - * If 'force' is not set, WAL stats message is only sent if enough time has - * passed since last one was sent to reach PGSTAT_STAT_INTERVAL. + * If the processes that generate WAL data must call pgstat_report_wal() instead. + * + * If 'force' is not set, the WAL stats message is only sent if the statistics + * counters except for the counters related to generated WAL data were updated + * and enough time has passed since last one was sent to reach PGSTAT_STAT_INTERVAL. * * Return true if the message is sent, and false otherwise. * ---------- @@ -4723,26 +4732,32 @@ pgstat_report_wal(void) bool pgstat_send_wal(bool force) { - /* We assume this initializes to zeroes */ - static const PgStat_MsgWal all_zeroes; static TimestampTz sendTime = 0; - /* - * This function can be called even if nothing at all has happened. In - * this case, avoid sending a completely empty message to the stats - * collector. - */ - if (memcmp(&WalStats, &all_zeroes, sizeof(PgStat_MsgWal)) == 0) - return false; - if (!force) { - TimestampTz now = GetCurrentTimestamp(); + TimestampTz now; + + /* + * Don't expend a clock check if the WAL statistics counters were not + * updated. + * + * We don't consider the WAL stats related to the generated WAL data + * because pgstat_report_wal() is called instead in the case. + * + * We can know whether the counters were updated to check only two + * records. So, for performance, we don't allocate another memory + * spaces and check the all stats like pgstat_send_slru(). + */ + if (walStats.wal_write == 0 && walStats.wal_sync == 0) + return false; /* * Don't send a message unless it's been at least PGSTAT_STAT_INTERVAL - * msec since we last sent one. + * msec since we last sent one to avoid overloading the stats + * collector. */ + now = GetCurrentTimestamp(); if (!TimestampDifferenceExceeds(sendTime, now, PGSTAT_STAT_INTERVAL)) return false; sendTime = now; ^ permalink raw reply [nested|flat] 8698+ messages in thread
* Re: wal stats questions @ 2021-03-30 08:28 Kyotaro Horiguchi <[email protected]> parent: Masahiro Ikeda <[email protected]> 0 siblings, 1 reply; 8698+ messages in thread From: Kyotaro Horiguchi @ 2021-03-30 08:28 UTC (permalink / raw) To: [email protected]; +Cc: pgsql-hackers; [email protected]; [email protected] At Tue, 30 Mar 2021 09:41:24 +0900, Masahiro Ikeda <[email protected]> wrote in > I update the patch since there were my misunderstanding points. > > On 2021/03/26 16:20, Masahiro Ikeda wrote: > > Thanks for many your suggestions! > > I made the patch to handle the issues. > > > >> 1) What is the motivation to have both prevWalUsage and pgWalUsage, > >> instead of just accumulating the stats since the last submission? > >> There doesn't seem to be any comment explaining it? Computing > >> differences to previous values, and copying to prev*, isn't free. I > >> assume this is out of a fear that the stats could get reset before > >> they're used for instrument.c purposes - but who knows? > > > > I removed the unnecessary code copying pgWalUsage and just reset the > > pgWalUsage after reporting the stats in pgstat_report_wal(). > > I didn't change this. > > >> 2) Why is there both pgstat_send_wal() and pgstat_report_wal()? With the > >> former being used by wal writer, the latter by most other processes? > >> There again don't seem to be comments explaining this. > > > > I added the comments why two functions are separated. > > (But is it better to merge them?) > > I updated the comments for following reasons. > > > >> 3) Doing if (memcmp(&WalStats, &all_zeroes, sizeof(PgStat_MsgWal)) == 0) > >> just to figure out if there's been any changes isn't all that > >> cheap. This is regularly exercised in read-only workloads too. Seems > >> adding a boolean WalStats.have_pending = true or such would be > >> better. > >> 4) For plain backends pgstat_report_wal() is called by > >> pgstat_report_stat() - but it is not checked as part of the "Don't > >> expend a clock check if nothing to do" check at the top. It's > >> probably rare to have pending wal stats without also passing one of > >> the other conditions, but ... > > > > I added the logic to check if the stats counters are updated or not in > > pgstat_report_stat() using not only generated wal record but also write/sync > > counters, and it can skip to call reporting function. > > I removed the checking code whether the wal stats counters were updated or not > in pgstat_report_stat() since I couldn't understand the valid case yet. > pgstat_report_stat() is called by backends when the transaction is finished. > This means that the condition seems always pass. Doesn't the same holds for all other counters? If you are saying that "wal counters should be zero if all other stats counters are zero", we need an assertion to check that and a comment to explain that. I personally find it safer to add the WAL-stats condition to the fast-return check, rather than addin such assertion. pgstat_send_wal() is called mainly from pgstat_report_wal() which consumes pgWalStats counters and WalWriterMain() which doesn't. Checking on pgWalStats counters isn't so complex that we need to avoid that in wal writer, thus *I* think pgstat_send_wal() and pgstat_report_wal() can be consolidated. Even if you have a strong opinion that wal writer should call a separate function, the name should be something other than pgstat_send_wal() since it ignores pgWalUsage counters, which are supposed to be included in "WAL stats". > I thought to implement if the WAL stats counters were not updated, skip to > send all statistics including the counters for databases and so on. But I > think it's not good because it may take more time to be reflected the > generated stats by read-only transaction. Ur, yep. > > Although I added the condition which the write/sync counters are updated or > > not, I haven't understood the following case yet...Sorry. I checked related > > code and tested to insert large object, but I couldn't. I'll investigate more > > deeply, but if you already know the function which leads the following case, > > please let me know. > > I understood the above case (Fujii-san, thanks for your advice in person). > When to flush buffers, for example, to select buffer replacement victim, > it requires a WAL flush if the buffer is dirty. So, to check the WAL stats > counters are updated or not, I check the number of generated wal record and > the counter of syncing in pgstat_report_wal(). > > The reason why not to check the counter of writing is that if to write is > happened, to sync is happened too in the above case. I added the comments in > the patch. Mmm.. Although I couldn't read you clearly, The fact that a flush may happen without a write means the reverse at the same time, a write may happen without a flush. For asynchronous commits, WAL-write happens alone unaccompanied by a flush. And the corresponding flush would happen later without writes. regards. -- Kyotaro Horiguchi NTT Open Source Software Center ^ permalink raw reply [nested|flat] 8698+ messages in thread
* Re: wal stats questions @ 2021-03-30 11:37 Masahiro Ikeda <[email protected]> parent: Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Masahiro Ikeda @ 2021-03-30 11:37 UTC (permalink / raw) To: Kyotaro Horiguchi <[email protected]>; +Cc: pgsql-hackers; [email protected]; [email protected] On 2021/03/30 17:28, Kyotaro Horiguchi wrote: > At Tue, 30 Mar 2021 09:41:24 +0900, Masahiro Ikeda <[email protected]> wrote in >> I update the patch since there were my misunderstanding points. >> >> On 2021/03/26 16:20, Masahiro Ikeda wrote: >>> Thanks for many your suggestions! >>> I made the patch to handle the issues. >>> >>>> 1) What is the motivation to have both prevWalUsage and pgWalUsage, >>>> instead of just accumulating the stats since the last submission? >>>> There doesn't seem to be any comment explaining it? Computing >>>> differences to previous values, and copying to prev*, isn't free. I >>>> assume this is out of a fear that the stats could get reset before >>>> they're used for instrument.c purposes - but who knows? >>> >>> I removed the unnecessary code copying pgWalUsage and just reset the >>> pgWalUsage after reporting the stats in pgstat_report_wal(). >> >> I didn't change this. >> >>>> 2) Why is there both pgstat_send_wal() and pgstat_report_wal()? With the >>>> former being used by wal writer, the latter by most other processes? >>>> There again don't seem to be comments explaining this. >>> >>> I added the comments why two functions are separated. >>> (But is it better to merge them?) >> >> I updated the comments for following reasons. >> >> >>>> 3) Doing if (memcmp(&WalStats, &all_zeroes, sizeof(PgStat_MsgWal)) == 0) >>>> just to figure out if there's been any changes isn't all that >>>> cheap. This is regularly exercised in read-only workloads too. Seems >>>> adding a boolean WalStats.have_pending = true or such would be >>>> better. >>>> 4) For plain backends pgstat_report_wal() is called by >>>> pgstat_report_stat() - but it is not checked as part of the "Don't >>>> expend a clock check if nothing to do" check at the top. It's >>>> probably rare to have pending wal stats without also passing one of >>>> the other conditions, but ... >>> >>> I added the logic to check if the stats counters are updated or not in >>> pgstat_report_stat() using not only generated wal record but also write/sync >>> counters, and it can skip to call reporting function. >> >> I removed the checking code whether the wal stats counters were updated or not >> in pgstat_report_stat() since I couldn't understand the valid case yet. >> pgstat_report_stat() is called by backends when the transaction is finished. >> This means that the condition seems always pass. > > Doesn't the same holds for all other counters? If you are saying that > "wal counters should be zero if all other stats counters are zero", we > need an assertion to check that and a comment to explain that. > > I personally find it safer to add the WAL-stats condition to the > fast-return check, rather than addin such assertion. Thanks for your comments. OK, I added the condition to the fast-return check. I noticed that I misunderstood that the purpose is to avoid expanding a clock check using WAL stats counters. But, the purpose is to make the conditions stricter, right? > pgstat_send_wal() is called mainly from pgstat_report_wal() which > consumes pgWalStats counters and WalWriterMain() which > doesn't. Checking on pgWalStats counters isn't so complex that we need > to avoid that in wal writer, thus *I* think pgstat_send_wal() and > pgstat_report_wal() can be consolidated. Even if you have a strong > opinion that wal writer should call a separate function, the name > should be something other than pgstat_send_wal() since it ignores > pgWalUsage counters, which are supposed to be included in "WAL stats". OK, I consolidated them. >> I thought to implement if the WAL stats counters were not updated, skip to >> send all statistics including the counters for databases and so on. But I >> think it's not good because it may take more time to be reflected the >> generated stats by read-only transaction. > > Ur, yep. > >>> Although I added the condition which the write/sync counters are updated or >>> not, I haven't understood the following case yet...Sorry. I checked related >>> code and tested to insert large object, but I couldn't. I'll investigate more >>> deeply, but if you already know the function which leads the following case, >>> please let me know. >> >> I understood the above case (Fujii-san, thanks for your advice in person). >> When to flush buffers, for example, to select buffer replacement victim, >> it requires a WAL flush if the buffer is dirty. So, to check the WAL stats >> counters are updated or not, I check the number of generated wal record and >> the counter of syncing in pgstat_report_wal(). >> >> The reason why not to check the counter of writing is that if to write is >> happened, to sync is happened too in the above case. I added the comments in >> the patch. > > Mmm.. Although I couldn't read you clearly, The fact that a flush may > happen without a write means the reverse at the same time, a write may > happen without a flush. For asynchronous commits, WAL-write happens > alone unaccompanied by a flush. And the corresponding flush would > happen later without writes. Sorry, I didn't explain it enough. For processes which may generate WAL records like backends, I thought it's enough to check (1)the number of generated WAL records and (2)the counters of syncing(flushing) the WAL. This is checked in pgstat_report_wal(). Sorry for that I didn't mention (1) in the above thread. If a backend execute a write transaction, some WAL records must be generated. So, it's ok to check (1) only regardless of whether asynchronous commit is enabled or not. OHOT, if a backend execute a read-only transaction, WAL records won't be generated (although HOT makes a wal records exactly...). But, WAL-write and flush may happen when to flush buffers via XLogFlush(). In this case, if WAL-write happened, flush must be happen later. But, if my understanding is correct, there is no a case to flush doesn't happen, but to write happen. So, I thought (2) is needed and it's enough to check the counter of syncing(flushing). Regards, -- Masahiro Ikeda NTT DATA CORPORATION Attachments: [text/x-patch] v3-0001-performance-improvements-of-reporting-wal-stats.patch (7.5K, ../../[email protected]/2-v3-0001-performance-improvements-of-reporting-wal-stats.patch) download | inline diff: diff --git a/src/backend/executor/instrument.c b/src/backend/executor/instrument.c index 237e13361b..15eb3c8e64 100644 --- a/src/backend/executor/instrument.c +++ b/src/backend/executor/instrument.c @@ -19,6 +19,17 @@ BufferUsage pgBufferUsage; static BufferUsage save_pgBufferUsage; + +/* + * generated WAL usage counters. + * + * Be careful that the counters are cleared after reporting them to + * the stats collector although you can use WalUsageAccumDiff() + * to computing differences to previous values. For backends, + * the counters may be reset after a transaction is finished and + * pgstat_send_wal() is invoked, so you can compute the difference + * in the same transaction only. + */ WalUsage pgWalUsage; static WalUsage save_pgWalUsage; diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c index cdd07770a0..75a95f3de7 100644 --- a/src/backend/postmaster/checkpointer.c +++ b/src/backend/postmaster/checkpointer.c @@ -505,7 +505,7 @@ CheckpointerMain(void) pgstat_send_bgwriter(); /* Send WAL statistics to the stats collector. */ - pgstat_report_wal(); + pgstat_send_wal(true); /* * If any checkpoint flags have been set, redo the loop to handle the @@ -583,7 +583,7 @@ HandleCheckpointerInterrupts(void) BgWriterStats.m_requested_checkpoints++; ShutdownXLOG(0, 0); pgstat_send_bgwriter(); - pgstat_report_wal(); + pgstat_send_wal(true); /* Normal exit from the checkpointer is here */ proc_exit(0); /* done */ diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c index 60f45ccc4e..7fd03b69b4 100644 --- a/src/backend/postmaster/pgstat.c +++ b/src/backend/postmaster/pgstat.c @@ -144,14 +144,6 @@ char *pgstat_stat_tmpname = NULL; PgStat_MsgBgWriter BgWriterStats; PgStat_MsgWal WalStats; -/* - * WAL usage counters saved from pgWALUsage at the previous call to - * pgstat_report_wal(). This is used to calculate how much WAL usage - * happens between pgstat_report_wal() calls, by substracting - * the previous counters from the current ones. - */ -static WalUsage prevWalUsage; - /* * List of SLRU names that we keep stats for. There is no central registry of * SLRUs, so we use this fixed list instead. The "other" entry is used for @@ -879,9 +871,19 @@ pgstat_report_stat(bool disconnect) TabStatusArray *tsa; int i; - /* Don't expend a clock check if nothing to do */ + /* + * Don't expend a clock check if nothing to do. + * + * Note: regarding to WAL statistics counters, it's not enough to check + * only whether the wal record is generated or not. If a read transaction + * is executed, wal records aren't nomally generated (although HOT makes + * wal records). But, just writes and syncs the wal data may happen when + * to flush buffers. + */ if ((pgStatTabList == NULL || pgStatTabList->tsa_used == 0) && pgStatXactCommit == 0 && pgStatXactRollback == 0 && + pgWalUsage.wal_records == 0 && walStats.wal_write == 0 && + walStats.wal_sync == 0 && !have_function_stats && !disconnect) return; @@ -975,7 +977,7 @@ pgstat_report_stat(bool disconnect) pgstat_send_funcstats(); /* Send WAL statistics */ - pgstat_report_wal(); + pgstat_send_wal(true); /* Finally send SLRU statistics */ pgstat_send_slru(); @@ -3117,13 +3119,6 @@ pgstat_initialize(void) MyBEEntry = &BackendStatusArray[MaxBackends + MyAuxProcType]; } - /* - * Initialize prevWalUsage with pgWalUsage so that pgstat_report_wal() can - * calculate how much pgWalUsage counters are increased by substracting - * prevWalUsage from pgWalUsage. - */ - prevWalUsage = pgWalUsage; - /* Set up a process-exit hook to clean up */ on_shmem_exit(pgstat_beshutdown_hook, 0); } @@ -4671,44 +4666,6 @@ pgstat_send_bgwriter(void) MemSet(&BgWriterStats, 0, sizeof(BgWriterStats)); } -/* ---------- - * pgstat_report_wal() - - * - * Calculate how much WAL usage counters are increased and send - * WAL statistics to the collector. - * - * Must be called by processes that generate WAL. - * ---------- - */ -void -pgstat_report_wal(void) -{ - WalUsage walusage; - - /* - * Calculate how much WAL usage counters are increased by substracting the - * previous counters from the current ones. Fill the results in WAL stats - * message. - */ - MemSet(&walusage, 0, sizeof(WalUsage)); - WalUsageAccumDiff(&walusage, &pgWalUsage, &prevWalUsage); - - WalStats.m_wal_records = walusage.wal_records; - WalStats.m_wal_fpi = walusage.wal_fpi; - WalStats.m_wal_bytes = walusage.wal_bytes; - - /* - * Send WAL stats message to the collector. - */ - if (!pgstat_send_wal(true)) - return; - - /* - * Save the current counters for the subsequent calculation of WAL usage. - */ - prevWalUsage = pgWalUsage; -} - /* ---------- * pgstat_send_wal() - * @@ -4720,20 +4677,28 @@ pgstat_report_wal(void) * Return true if the message is sent, and false otherwise. * ---------- */ -bool +void pgstat_send_wal(bool force) { - /* We assume this initializes to zeroes */ - static const PgStat_MsgWal all_zeroes; static TimestampTz sendTime = 0; /* - * This function can be called even if nothing at all has happened. In - * this case, avoid sending a completely empty message to the stats - * collector. + * First, to check the WAL stats counters were updated. + * + * Even if the 'force' is true, we don't need to send the stats if the + * counters were not updated. + * + * We can know whether the counters were updated or not to check only + * three counters. So, for performance, we don't allocate another memory + * spaces and check the all stats like pgstat_send_slru(). + * + * 'wal_records' is zero means that wal records weren't generated. So, + * 'wal_fpi', 'wal_bytes', 'm_wal_buffers_full' is zero too. 'wal_writes' + * and 'wal_sync' are zero means the counter of time spent is zero too. */ - if (memcmp(&WalStats, &all_zeroes, sizeof(PgStat_MsgWal)) == 0) - return false; + if (pgWalUsage.wal_records == 0 && walStats.wal_write == 0 && + walStats.wal_sync == 0) + return; if (!force) { @@ -4741,13 +4706,21 @@ pgstat_send_wal(bool force) /* * Don't send a message unless it's been at least PGSTAT_STAT_INTERVAL - * msec since we last sent one. + * msec since we last sent one to avoid overloading the stats + * collector. */ if (!TimestampDifferenceExceeds(sendTime, now, PGSTAT_STAT_INTERVAL)) - return false; + return; sendTime = now; } + /* + * set the counters related to generated WAL data. + */ + WalStats.m_wal_records = pgWalUsage.wal_records; + WalStats.m_wal_fpi = pgWalUsage.wal_fpi; + WalStats.m_wal_bytes = pgWalUsage.wal_bytes; + /* * Prepare and send the message */ @@ -4759,7 +4732,14 @@ pgstat_send_wal(bool force) */ MemSet(&WalStats, 0, sizeof(WalStats)); - return true; + /* + * Clear out the statistics for generated wal usage too. + * + * Although these counters are used in another places, for example in + * pg_stat_statements.c, it's ok to clear out because no one takes + * difference crossing pgstat_send_wal() calls. + */ + MemSet(&pgWalUsage, 0, sizeof(WalUsage)); } /* ---------- diff --git a/src/include/pgstat.h b/src/include/pgstat.h index 87672e6f30..2174a7439c 100644 --- a/src/include/pgstat.h +++ b/src/include/pgstat.h @@ -1601,8 +1601,7 @@ extern void pgstat_twophase_postabort(TransactionId xid, uint16 info, extern void pgstat_send_archiver(const char *xlog, bool failed); extern void pgstat_send_bgwriter(void); -extern void pgstat_report_wal(void); -extern bool pgstat_send_wal(bool force); +extern void pgstat_send_wal(bool force); /* ---------- * Support functions for the SQL-callable functions to ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..97ea882cf71 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index 00b21ede481..c25dbeadff3 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -233,6 +234,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 0f6b5df322c..16009fa75a4 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1470,7 +1471,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index fe6bfeba25e..0d415f5f8f2 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1776,9 +1777,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin + * is not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..49d1bf4bfac 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --=-=-=-- ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v50 7/8] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --brnevsqjnuzpyok4 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v50-0008-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v52 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --gp2pyozrd5pweboh Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v52-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
* [PATCH v51 08/10] Introduce an option to make logical replication database specific. @ 2026-04-03 10:34 Antonin Houska <[email protected]> 0 siblings, 0 replies; 8698+ messages in thread From: Antonin Houska @ 2026-04-03 10:34 UTC (permalink / raw) By default, the logical decoding assumes access to shared catalogs, so the snapshot builder needs to consider cluster-wide XIDs during startup. That in turn means that, if any transaction is already running (and has XID assigned), the snapshot builder needs to wait for its completion, as it does not know if that transaction performed catalog changes earlier. Possible problem with this concept is that if REPACK (CONCURRENTLY) is running in some database, backends running the same command in other databases get stuck until the first one has committed. Thus only as single backend in the cluster can run REPACK (CONCURRENTLY) at any time. Likewise, REPACK (CONCURRENTLY) can block walsenders starting on behalf of subscriptions throughout the cluster. This patch introduces the possibility for a backend to declare that its output plugin does not use shared catalogs (i.e. catalogs that can be changed by transactions running in other databases in the cluster). In that case, no snapshot the backend will use during the decoding needs to contain information about transactions running in other databases. Thus the snapshot builder only needs to wait for completion of transactions in the current database. Currently we only use this option in the REPACK background worker. It could possibly be used in walsender involved in logical replication too, however that would need thorough analysis of its output plugin. The patch bumps WAL version number, due to a new field in xl_running_xacts. --- contrib/pg_visibility/pg_visibility.c | 4 ++-- src/backend/access/index/genam.c | 18 ++++++++++++++++ src/backend/access/rmgrdesc/standbydesc.c | 2 ++ src/backend/access/transam/xlog.c | 2 +- src/backend/access/transam/xlogfuncs.c | 2 +- src/backend/commands/repack_worker.c | 8 +++++++ src/backend/postmaster/bgwriter.c | 2 +- src/backend/replication/logical/snapbuild.c | 10 ++++++++- src/backend/replication/slot.c | 12 +++++++++-- src/backend/storage/ipc/procarray.c | 23 ++++++++++++++++++++- src/backend/storage/ipc/standby.c | 14 +++++++++++-- src/include/access/genam.h | 8 +++++++ src/include/access/xlog_internal.h | 2 +- src/include/storage/procarray.h | 2 +- src/include/storage/standby.h | 3 ++- src/include/storage/standbydefs.h | 1 + 16 files changed, 99 insertions(+), 14 deletions(-) diff --git a/contrib/pg_visibility/pg_visibility.c b/contrib/pg_visibility/pg_visibility.c index dfab0b64cf5..d564bd2a00c 100644 --- a/contrib/pg_visibility/pg_visibility.c +++ b/contrib/pg_visibility/pg_visibility.c @@ -621,7 +621,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) else if (rel == NULL || rel->rd_rel->relisshared) { /* Shared relation: take into account all running xids */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestRunningXid; @@ -632,7 +632,7 @@ GetStrictOldestNonRemovableTransactionId(Relation rel) * Normal relation: take into account xids running within the current * database */ - runningTransactions = GetRunningTransactionData(); + runningTransactions = GetRunningTransactionData(InvalidOid); LWLockRelease(ProcArrayLock); LWLockRelease(XidGenLock); return runningTransactions->oldestDatabaseRunningXid; diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 1408989c568..df092dc999a 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -37,6 +37,14 @@ #include "utils/ruleutils.h" #include "utils/snapmgr.h" +/* + * If a backend is going to do logical decoding and if the output plugin does + * not need to access shared catalogs, setting this variable to false can make + * the decoding startup faster. In particular, the backend will not need to + * wait for completion of already running transactions in other databases. + */ +bool accessSharedCatalogsInDecoding = true; + /* ---------------------------------------------------------------- * general access method routines @@ -394,6 +402,16 @@ systable_beginscan(Relation heapRelation, SysScanDesc sysscan; Relation irel; + /* + * If this backend promised that it won't access shared catalogs during + * logical decoding, this seems to be the right place to check. + * + * XXX Should this be ereport(ERROR) ? + */ + Assert(!HistoricSnapshotActive() || + accessSharedCatalogsInDecoding || + !heapRelation->rd_rel->relisshared); + if (indexOK && !IgnoreSystemIndexes && !ReindexIsProcessingIndex(indexId)) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 0a291354ae2..685d1bdb024 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -41,6 +41,8 @@ standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) for (i = 0; i < xlrec->subxcnt; i++) appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); } + + appendStringInfo(buf, "; dbid: %u", xlrec->dbid); } void diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 2c1c6f88b74..8da8eff93e4 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7336,7 +7336,7 @@ CreateCheckPoint(int flags) * recovery we don't need to write running xact data. */ if (!shutdown && XLogStandbyInfoActive()) - LogStandbySnapshot(); + LogStandbySnapshot(InvalidOid); START_CRIT_SECTION(); diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c index 65bbaeda59c..0f5979691e6 100644 --- a/src/backend/access/transam/xlogfuncs.c +++ b/src/backend/access/transam/xlogfuncs.c @@ -245,7 +245,7 @@ pg_log_standby_snapshot(PG_FUNCTION_ARGS) (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("pg_log_standby_snapshot() can only be used if \"wal_level\" >= \"replica\""))); - recptr = LogStandbySnapshot(); + recptr = LogStandbySnapshot(InvalidOid); /* * As a convenience, return the WAL location of the last inserted record diff --git a/src/backend/commands/repack_worker.c b/src/backend/commands/repack_worker.c index c85166ba849..ff34e246469 100644 --- a/src/backend/commands/repack_worker.c +++ b/src/backend/commands/repack_worker.c @@ -16,6 +16,7 @@ */ #include "postgres.h" +#include "access/genam.h" #include "access/table.h" #include "access/xlog_internal.h" #include "access/xlogutils.h" @@ -237,6 +238,13 @@ repack_setup_logical_decoding(Oid relid) EnsureLogicalDecodingEnabled(); + /* + * By declaring that our output plugin does not need shared catalogs, we + * avoid waiting for completion of transactions running in other databases + * than the one we're connected to. + */ + accessSharedCatalogsInDecoding = false; + /* * Neither prepare_write nor do_write callback nor update_progress is * useful for us. diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c index 1d8947774a9..a30de4262eb 100644 --- a/src/backend/postmaster/bgwriter.c +++ b/src/backend/postmaster/bgwriter.c @@ -289,7 +289,7 @@ BackgroundWriterMain(const void *startup_data, size_t startup_data_len) if (now >= timeout && last_snapshot_lsn <= GetLastImportantRecPtr()) { - last_snapshot_lsn = LogStandbySnapshot(); + last_snapshot_lsn = LogStandbySnapshot(InvalidOid); last_snapshot_ts = now; } } diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index b4269a3b102..2e3926e1d13 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -125,6 +125,7 @@ #include <sys/stat.h> #include <unistd.h> +#include "access/genam.h" #include "access/heapam_xlog.h" #include "access/transam.h" #include "access/xact.h" @@ -1465,7 +1466,14 @@ SnapBuildWaitSnapshot(xl_running_xacts *running, TransactionId cutoff) */ if (!RecoveryInProgress()) { - LogStandbySnapshot(); + Oid dbid; + + /* + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + LogStandbySnapshot(dbid); } } diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c index a9092fc2382..d553bd5dbff 100644 --- a/src/backend/replication/slot.c +++ b/src/backend/replication/slot.c @@ -39,6 +39,7 @@ #include <unistd.h> #include <sys/stat.h> +#include "access/genam.h" #include "access/transam.h" #include "access/xlog_internal.h" #include "access/xlogrecovery.h" @@ -1760,9 +1761,16 @@ ReplicationSlotReserveWal(void) if (!RecoveryInProgress() && SlotIsLogical(slot)) { XLogRecPtr flushptr; + Oid dbid; - /* make sure we have enough information to start */ - flushptr = LogStandbySnapshot(); + /* + * Make sure we have enough information to start. + * + * Only consider transactions of the current database if our plugin is + * not supposed to access shared catalogs. + */ + dbid = accessSharedCatalogsInDecoding ? InvalidOid : MyDatabaseId; + flushptr = LogStandbySnapshot(dbid); /* and make sure it's fsynced to disk */ XLogFlush(flushptr); diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index cc207cb56e3..92ed34128e5 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -2631,9 +2631,11 @@ ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc) * * Note that if any transaction has overflowed its cached subtransactions * then there is no real need include any subtransactions. + * + * If 'dbid' is valid, only gather transactions running in that database. */ RunningTransactions -GetRunningTransactionData(void) +GetRunningTransactionData(Oid dbid) { /* result workspace */ static RunningTransactionsData CurrentRunningXactsData; @@ -2708,6 +2710,18 @@ GetRunningTransactionData(void) if (!TransactionIdIsValid(xid)) continue; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid)) + { + int pgprocno = arrayP->pgprocnos[index]; + PGPROC *proc = &allProcs[pgprocno]; + + if (proc->databaseId != dbid) + continue; + } + /* * Be careful not to exclude any xids before calculating the values of * oldestRunningXid and suboverflowed, since these are used to clean @@ -2758,6 +2772,12 @@ GetRunningTransactionData(void) PGPROC *proc = &allProcs[pgprocno]; int nsubxids; + /* + * Filter by database OID if requested. + */ + if (OidIsValid(dbid) && proc->databaseId != dbid) + continue; + /* * Save subtransaction XIDs. Other backends can't add or remove * entries while we're holding XidGenLock. @@ -2791,6 +2811,7 @@ GetRunningTransactionData(void) * increases if slots do. */ + CurrentRunningXacts->dbid = dbid; CurrentRunningXacts->xcnt = count - subcount; CurrentRunningXacts->subxcnt = subcount; CurrentRunningXacts->subxid_status = suboverflowed ? SUBXIDS_IN_SUBTRANS : SUBXIDS_IN_ARRAY; diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index de9092fdf5b..c653ea742bc 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1188,6 +1188,14 @@ standby_redo(XLogReaderState *record) xl_running_xacts *xlrec = (xl_running_xacts *) XLogRecGetData(record); RunningTransactionsData running; + /* + * Records issued for specific database are not suitable for physical + * replication because that affects the whole cluster. In particular, + * the list of XID is probably incomplete here. + */ + if (OidIsValid(xlrec->dbid)) + return; + running.xcnt = xlrec->xcnt; running.subxcnt = xlrec->subxcnt; running.subxid_status = xlrec->subxid_overflow ? SUBXIDS_MISSING : SUBXIDS_IN_ARRAY; @@ -1277,11 +1285,12 @@ standby_redo(XLogReaderState *record) * as there's no independent knob to just enable logical decoding. For * details of how this is used, check snapbuild.c's introductory comment. * + * If 'dbid' is valid, only gather transactions running in that database. * * Returns the RecPtr of the last inserted record. */ XLogRecPtr -LogStandbySnapshot(void) +LogStandbySnapshot(Oid dbid) { XLogRecPtr recptr; RunningTransactions running; @@ -1314,7 +1323,7 @@ LogStandbySnapshot(void) * Log details of all in-progress transactions. This should be the last * record we write, because standby will open up when it sees this. */ - running = GetRunningTransactionData(); + running = GetRunningTransactionData(dbid); /* * GetRunningTransactionData() acquired ProcArrayLock, we must release it. @@ -1358,6 +1367,7 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; + xlrec.dbid = CurrRunningXacts->dbid; xlrec.xcnt = CurrRunningXacts->xcnt; xlrec.subxcnt = CurrRunningXacts->subxcnt; xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); diff --git a/src/include/access/genam.h b/src/include/access/genam.h index b69320a7fc8..56c573399ab 100644 --- a/src/include/access/genam.h +++ b/src/include/access/genam.h @@ -136,6 +136,14 @@ typedef struct IndexOrderByDistance bool isnull; } IndexOrderByDistance; +/* + * Is the backend interested in shared catalogs when performing logical + * decoding? + * + * XXX Is there a better place for this declaration? + */ +extern bool accessSharedCatalogsInDecoding; + /* * generalized index_ interface routines (in indexam.c) */ diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h index 755835d63bf..ae19982d88d 100644 --- a/src/include/access/xlog_internal.h +++ b/src/include/access/xlog_internal.h @@ -31,7 +31,7 @@ /* * Each page of XLOG file has a header like this: */ -#define XLOG_PAGE_MAGIC 0xD11E /* can be used as WAL version indicator */ +#define XLOG_PAGE_MAGIC 0xD11F /* can be used as WAL version indicator */ typedef struct XLogPageHeaderData { diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h index abdf021e66e..377b3060b9f 100644 --- a/src/include/storage/procarray.h +++ b/src/include/storage/procarray.h @@ -49,7 +49,7 @@ extern bool ProcArrayInstallImportedXmin(TransactionId xmin, VirtualTransactionId *sourcevxid); extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc); -extern RunningTransactions GetRunningTransactionData(void); +extern RunningTransactions GetRunningTransactionData(Oid dbid); extern bool TransactionIdIsInProgress(TransactionId xid); extern TransactionId GetOldestNonRemovableTransactionId(Relation rel); diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index 6a314c693cd..8715c08e94f 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -126,6 +126,7 @@ typedef enum typedef struct RunningTransactionsData { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ subxids_array_status subxid_status; @@ -143,7 +144,7 @@ typedef RunningTransactionsData *RunningTransactions; extern void LogAccessExclusiveLock(Oid dbOid, Oid relOid); extern void LogAccessExclusiveLockPrepare(void); -extern XLogRecPtr LogStandbySnapshot(void); +extern XLogRecPtr LogStandbySnapshot(Oid dbid); extern void LogStandbyInvalidations(int nmsgs, SharedInvalidationMessage *msgs, bool relcacheInitFileInval); diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index 231d251fd51..e75b7078766 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -46,6 +46,7 @@ typedef struct xl_standby_locks */ typedef struct xl_running_xacts { + Oid dbid; /* only track xacts in this database */ int xcnt; /* # of xact ids in xids[] */ int subxcnt; /* # of subxact ids in xids[] */ bool subxid_overflow; /* snapshot overflowed, subxids missing */ -- 2.47.3 --r2slln3zpmilwu22 Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename="v51-0009-Reserve-replication-slots-specifically-for-REPAC.patch" ^ permalink raw reply [nested|flat] 8698+ messages in thread
end of thread, other threads:[~2026-04-03 10:34 UTC | newest] Thread overview: 8698+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2021-03-24 23:22 wal stats questions Andres Freund <[email protected]> 2021-03-25 01:51 ` Masahiro Ikeda <[email protected]> 2021-03-25 04:07 ` Andres Freund <[email protected]> 2021-03-25 07:37 ` Kyotaro Horiguchi <[email protected]> 2021-03-25 10:01 ` Fujii Masao <[email protected]> 2021-03-26 01:08 ` Kyotaro Horiguchi <[email protected]> 2021-03-26 01:32 ` Fujii Masao <[email protected]> 2021-03-26 03:47 ` Kyotaro Horiguchi <[email protected]> 2021-03-26 07:20 ` Masahiro Ikeda <[email protected]> 2021-03-30 00:41 ` Masahiro Ikeda <[email protected]> 2021-03-30 08:28 ` Kyotaro Horiguchi <[email protected]> 2021-03-30 11:37 ` Masahiro Ikeda <[email protected]> 2021-03-26 17:07 ` Andres Freund <[email protected]> 2021-03-29 02:09 ` Kyotaro Horiguchi <[email protected]> 2021-03-29 02:11 ` Kyotaro Horiguchi <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v50 7/8] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v51 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]> 2026-04-03 10:34 [PATCH v52 08/10] Introduce an option to make logical replication database specific. Antonin Houska <[email protected]>
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